1. Field of the Invention
The instant disclosure relates to a control apparatus for switching phases in a DC motor; in particular, to a control apparatus and a control method thereof, which can dynamically adjust the tuning on or off of each switch of driving circuit via detecting the current value of the coil of the DC motor at the timing point when switching phases, so as to reduce the motor vibration noises and to increase the rotation speed or the efficiency.
2. Description of Related Art
In the traditional DC motor, the electrical phase switching is usually implemented by using the semi-conductor switches. Please refer to FIG. 1. FIG. 1 shows a schematic drawing of a driving circuit of a traditional DC motor. The driving circuit 10 is an H-bridge circuit comprising four switches Q1˜Q4, which is electrically connected to the DC motor 12 respectively via its two output ends A and B. Moreover, during the operation of the driving circuit 10, there are mainly two different turning phases, wherein a first phase refers to the condition that the switches Q1 and Q4 are turned on, and a second phase refers to the condition that the switches Q2 and Q3 are turned on. Thus, the driving circuit 10 needs to switch phases between these two phases to effectively drive the DC motor 12 to rotate.
Specifically speaking, please refer to FIG. 2. FIG. 2 shows a schematic drawing of a control circuit of a traditional DC motor. The control circuit 20 comprises four output ends AH, BH, AL and BL to respectively provide the switch signals H1, H2, L1 and L2 to control the turning on or off of each switch Q1˜Q4 in the driving circuit 10. Thus, at the first phase, the control circuit 20 uses the switch signals H1 and L2 to turn on the switches Q1 and Q4, and uses the switch signals H2 and L1 to turn off the switches Q3 and Q2, which makes the current Im flow from the output end A, through the DC motor 12, and to the output end B. On the other hand, at the second phase, the control circuit 20 uses the switch signals H1 and L2 to turn off the switches Q1 and Q4, and uses the switch signals H2 and L1 to turn on the switches Q3 and Q2, which makes the current Im flow from the output end B, through the DC motor 12, and to the output end A.
However, during the rotation of the DC motor 12, the equivalent motor load of the DC motor 12 can be represented by the coil conductance, the coil resistor and a reaction electromotive force having opposite polarity to the applied voltage. Thus, the current Im flowing through the DC motor 12 must be influenced by the above parameters, and changes correspondingly. Accordingly, during the phase switching, if the current Im cannot be effectively controlled, the current left at the timing point of phase switching would affect the operation of the DC motor 12, which makes the DC motor 12 produce mechanical noise during the rotation.